Climate change could hurt your dog as diseases spread to new areas

SAN FRANCISCO – As if this year's storms, floods and heat waves were not enough to worry you, some experts fear that climate change will also widen the distribution of heart-rending diseases or even kill dogs , which further exposes pets to the diseases of their owners have never had to deal with before.

Epidemiologists and veterinary biologists say that Rocky Mountain Fever, a bacterial disease that can cause fever, joint pain and vomiting, is spreading in California and Texas. The heartworm, which can damage the cardiovascular system and clog the heart, spreads beyond its traditional focus in the south and southeast. Lyme disease, which can cause joint swelling and lameness, is now affecting dogs as far north as Canada.

"Veterinarians need to know what's local. But what's happening changes so fast, how are you going to follow? Said Janet Foley, professor of epidemiology at the University of California, Davis, School of Veterinary Medicine.

Many of these diseases also affect humans, but since dogs spend a lot of time outdoors and in the vegetation, they can be particularly exposed.

The Earth is warming

Not all veterinarians are convinced that climate change of anthropogenic origin is one of the main drivers of the movement of animal diseases.

Warren Hess, deputy director of the American Veterinary Medical Association, said the spread of heartworm disease was increasing because of changes in the frequency with which dogs are moved across the country.

"With increasing social pressure to restrict the sale of dogs in pet stores, this has resulted in a dramatic increase in the number of dogs coming in from pet shelters to meet the demand," he said.

Natural disasters also play a role. "The greatest spread of heartworm disease in the United States has certainly followed the national distribution of dogs due to Hurricane Katrina in 2005," said Hess, whose responsibilities included disaster preparedness.

He said that as long as climate change occurs and will continue to occur, "it is important that we properly frame the discussions and use all available scientific data as we continue the discussion."

Certainly, it is not easy to make the link between the expansion or displacement of ticks carrying disease, infection rates and populations of local dogs. There is no mandatory reporting requirement, unlike some human diseases. Data on tick and mosquito distribution are patchy in many areas. The tests for some of the diseases that seem to be moving did not exist 10 years ago, so it's hard to judge their historical significance.

Nevertheless, many scientists see patterns and linkages that direct them to climate change as an important part of the observed changes.

"There is no smoking gun and there will never be a smoking gun. We try to connect two things that work at very different scales in time and space, "said Ram Raghavan, a professor of space epidemiology at the College of Veterinary Medicine at Kansas State University in Manhattan, Kansas.

And yet, he has documented significant changes in Midwest tick populations, both in terms of tick infestation intensity, surface area, and when ticks are active. For example, monitoring his team in western Kansas and Oklahoma found Lone Star ticks that did not live there. Ehrlichiosis, a disease that in dogs can cause bruising, nosebleeds and lameness.

"We believe that ticks do not exist in these areas, but we find them more and more in the last five years. So I'm pretty sure they've grown, "he said. "Tick-borne diseases have really increased. We go on the field and we see and find ticks more easily than in the past. "

To get to the bottom of things, you will need data that does not exist yet. Raghavan has written several grant proposals to the National Institutes of Health in the United States of America for funding for long-term studies, tests and in-depth analyzes.

"It does not matter who caused the climate change, the climate has changed. Let's get the emotion out of the debate and get answers, "he said.

In the last century, according to the US National Oceanic and Atmospheric Administration, the United States recorded an average temperature 1.5 degrees higher than in the previous century. In addition, levels of rain and humidity have changed in some areas. All of these factors affect the places where disease-carrying insects develop.

For veterinarians and biologists studying insect-borne diseases, the situation is changing not only for striking diseases, but also for the time being. The times of the year when dogs are potentially at risk change in some areas where summers simply become too hot to support the insects or diseases that they carry. But that does not stop the spread.

"Illnesses like Lyme disease, which were transmitted in the height of the summer months, could now peak in the spring and fall, because it's too hot in the summer. You therefore benefit from a longer transmission window, "said Andrew Dobson, professor of ecology and evolutionary biology at Princeton University in Princeton, NJ .

Spotted Rocky Mountain fever spreads

This means that more and more dog owners need to pay attention to diseases such as mountain spotted fever, a tick-borne bacterial disease that can cause disease and even kill humans and their canine companions.

The bacterium initially invades the bloodstream and then settles into the cells lining the blood vessels. The blood can then leak out from the blood vessels and settle under the skin or even in the brain. It can be treated with antibiotics if taken in time.

At UC Davis, Foley is studying his spread. Historically, most cases have been spread by the American dog and have occurred in the states of the South Atlantic and South Central, with North Carolina and Oklahoma accounting for the largest proportion.

However, she is tracking a new strain of ticks heading north. This tropical strain of the brown tick is present in many parts of the world. She is known in Florida, Texas, Arizona and Southern California from the United States, where she could have been introduced from Brazil and Mexico.

It can also carry Spotted Rocky Mountain fever. Cases now appear along the US-Mexico border in areas that have never had to deal with the disease before. The new tick has now reached northern Los Angeles. Foley expects him to go up the Central Valley of California to Sacramento, in the north of the country.

It is much more aggressive than the tick species we are used to in the United States.

"The hotter it gets, the more it bites. So, the hotter it gets, the more infections there are, "Foley said.

Heartworm cases on the rise

Dog owners must also do more to protect their dogs from heartworm. The parasitic worms called Dirofilaria immitis spread by the bite of a mosquito that carries them to the larval state.

It is a particularly macabre disease. Once a dog is infected with the larva, it can turn into a parasitic worm of several feet that invades the dog's cardiovascular system, damaging the arteries that carry blood from the heart to the lungs and blocks the blood flow to the lungs clots that they can cause.

To be passed from one dog to another, the larvae must develop at a specific infectious stage within the mosquito. The warmer it gets, the faster the larvae mature in a form that can be transferred from mosquitoes to dogs. At 71 degrees Celsius, this process can take between 16 and 20 days. According to Bruce Kornreich, a cardiologist and professor of veterinary medicine at Cornell University's College of Veterinary Medicine in New York, if it's 82 degrees, it only takes 11 to 12 days.

Heartworm has always been a problem in the South and Southeast. Probably due to climate change and other factors, environments further north can now support the mosquitoes that transmit it and the larvae that cause it.

Infections are on the rise. Christopher Rehm, a veterinarian practicing in Mobile, Alabama, and president of the American Heartworm Society, recorded a 21.7% increase in the number of dogs per veterinary clinic tested by veterinary clinic.

There are no accurate numbers on the number of deaths caused by heartworm in dogs each year, but it is well known that untreated infections shorten the life span of a dog.

"Based on my own anecdotal experience, I would cautiously estimate that dogs infected with heartworm lose a third of their lives if they are not treated properly and on time," said Rehm. .

As the parasite moves into new areas, homeowners may not always be aware of the need to monitor it. It's also a problem for many months of the year, said Foley.

"A warm winter means that mosquitoes do not die, so they are eager to leave in January and start spreading the heartworm," she said.

This means that pet owners in a wider area of ​​the United States must give their dogs preventative medications to prevent them from contracting heartworm. In addition, people living in areas where heartworm infections were only a problem last summer should now treat their dogs longer per year.

Since 2010, the American Heartworm Disease Association and the Federal Food and Drug Administration both recommend preventive treatment throughout the year because the disease is more prevalent and so devastating for dogs that suffer from it, Kornreich said. .

Even if the heartworm is caught and treated in time, the dogs suffer. "Once they've already had a heart infection, they're never the same again," Rehm said.

Lyme disease moves north

In addition to being a huge danger to the health of humans, Lyme disease can also harm dogs, causing lameness, fever and lethargy. It is mainly carried by the blacklegged tick, or deer tick, in the northeastern and by the western legged tick in the southern United States.

Both are moving.

"With Ixodes (blacklegged ticks) moving north from the United States to Canada, this is a clear example of how things are changing, "said Michael Yabsley, a professor at the University's College of Veterinary Medicine. from Georgia to Athens, Georgia.

Unfortunately, even if Lyme disease moves north, it does not decline in its historic region. In fact, infection rates in dogs are getting worse, said Yabsley, who studies wildlife diseases.

In 2018, in Columbia County, New York, 30% of dogs tested were positive for Lyme disease. It was 21% in Worcester County, Massachusetts and 20% in Ulster County, New York, according to data collected by the Companion Animal Parasite Council.

Changes "fast and ugly"

Some even fear that climate change will lead to new diseases never seen in canine companions. When ticks develop in new areas, they come into contact with new hosts and they may be carriers of new diseases – which they could spread to the animals they sting.

This may have already happened with two human diseases. the The Heartland virus was discovered in 2009 and has so far infected about 20 people in the Midwest. It can cause fever, fatigue, nausea and diarrhea. Almost all patients have been hospitalized and some have died, according to US Centers for Disease Control and Prevention.

The Bourbon virus was first identified in 2014 and has infected a limited number of people in the Midwest and South, some of whom have died, according to the CDC. It can cause fever, rashes, fatigue, body aches and vomiting.

This is a reminder that the changing climate will affect people and their pets in a way that they may not be prepared for, Dobson said.

"There is no debate about whether this happens or not," he said. "It's happening fast and it's ugly."

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